The Carolina Breast Cancer Study (CBCS) Phase III is a continuation of a successful SPORE-supported population-based study examining genetic and epidemiologic risk factors and characteristics of breast cancer with a focus on African-American (AA) and premenopausal breast cancer. Studies from the approximately 2000 breast cancer patients participating in CBCS Phases I and II demonstrated that patients with AA race and young age had a high prevalence ofthe poor prognosis Basal-like breast cancer, and conversely a low prevalence ofthe good prognosis Luminal A subtype. Additionally, reevaluafion of traditional risk factors suggested considerable heterogeneity in effects by subtype; unique genetic and lifestyle factor associations have been observed for basal-like breast cancer, sometimes with effects in the opposite direction as expected based on associations with overall breast cancer risk. Based on these results, we hypothesize that the higher incidence and mortality from breast cancer in younger African American women compared to white women is due to a combination of factors, including differences in tumor biology, access to care, and type of treatment received. Furthermore, we hypothesize that continued comprehensive investigation of these factors will identify specific clinical and public health interventions to lower breast cancer mortality. To identify the factors that are associated with each breast cancer subtype, CBCS Phase III was opened in 2008, expanding the previous 24-county catchment area of Phases l-ll to 44 counties across North Carolina, and will accrue an additional 1500 AA women and 1500 non-AA women by 2014. The goal of CBCS III is to identify determinants of disparities in breast cancer clinical outcomes, including biologic, racial, socioeconomic, behavioral factors, and to identify modifiable factors in clinical care (delivery and access) that address the causes of disparities. CBCS Phase III is beyond the scope of a single funding source and is broadly supported by the University and other mechanisms, however there are crucial translational implications of this project. Specifically, SPORE funding for gene expression profiling on the tumors (Aim 1), which will enable evaluation of differences in risk factors distribution by subtype (Aim 2), and will be used for collection of treatment and outcome data to assess survival outcomes (Aim 3). This study will provide a comprehensive picture ofthe biology and epidemiology of breast cancer and breast cancer disparities, from risk to survival.